Monday, April 23, 2007

Is frozen fish as good as "fresh"?

There is nothing I hate more than being wrong. That's why I research things to death to make sure that I am not wrong too often. When it does happen though, it's a great learning experience, like the one I just got on freezing fin fish.

I kept procrastinating posting my frozen fish findings, but a question that Matthew Amster-Burton, a columnist on Culinate.com has just posted on my How to store fish story has inspired me to finally get off my lazy butt and write up my frozen fish experiments.

I used to be of the conviction that frozen fish was ALWAYS worse than fresh. I know, I know -- Whole Foods and many fish cookbooks like to tell you that previously frozen fish can be even fresher than not previously frozen fish because it was frozen at the peak of freshness. Just so that I don't have to use the "not previously frozen" terminology (that just takes too long to type), I'll use the word "fresh" to refer to fish that did not undergo the freezing process. The question I'll try to answer is whether previously frozen fish can taste as good as fresh, not whether it's as safe to eat.

Why would I care? I can get plenty of excellent fresh fish here in Boston. The problem is that when it comes to eating fish raw, freshness is not the only thing you have to worry about. Parasites are another hazard. Depending on the fish, they might pose an extremely small risk (to read all about them, see my posts on parasites, parts 1 and part 2). But if you want to eliminate that risk completely by killing the parasites, the only way to do it is to freeze the fish for at least 7 days. Cooking kills them too, of course, but that doesn't help you much with sushi.

My attitude to raw fish is pretty laid back. But when I teach sushi classes, I want to give my students an extra precaution option. Some people don't want to take a risk of food-born illness, no matter how minuscule. When I am serving fin fish raw, I only use tuna, farm-raised salmon, farm-raised branzino, and farm-raised yellowtail. The only way to get yellowtail in Boston is flash frozen and shipped from Japan so parasites are not an issue for that one at all. The other fish are fresh, but the odds of them having parasites are practically zero, so I just buy them from a reputable market (The New Deal in Cambridge) and eat them. As far as the freshness of the fish goes, freezing does nothing for you. It doesn't kill bacteria, just temporarily stops it's growth, so freezing inferior fish does not make it "safe".

I used to think that all fish would be damaged by freezing. Fish is mostly made of water, and water expands during freezing. This tears the flesh of the fish and makes it mushy. To prepare for my sushi class, I froze piece after piece of different fish, and here are my findings -- different fish react to freezing differently. Fatty fish freeze relatively well, and their texture is barely affected. Lean fish turn to mush in their defrosted raw state and rubber when cooked.

In these pictures, farm-raised salmon (very fatty) and fluke (very lean) were frozen the same way for the same amount of time. After defrosting, the fluke was so soft, I could turn it into a puree with a chop stick.

But, salmon stayed just as resilient as it was before freezing.

The reason I was so surprised was that I've had previously frozen salmon before that was terrible, so I concluded that salmon doesn't freeze well. What I didn't take into account was that it was wild Coho and Sockeye Salmon that tasted awful. They are extremely lean compared to farm-raised Atlantic or King salmon and do turn to mush when frozen. So when you choose your salmon for freezing, go with Atlantic (always farm-raised) or King (farm-raised or wild).

Even if you choose a freezer-friendly fish for your sushi, you have to freeze it and defrost it properly. Remove the skin from the fillet, wrap it as tightly as possible in plastic wrap without bending it, then put it in a zip lock bag to make sure it's completely sealed. Freeze for 7 days, then move it to the fridge 24 hours before using. Do not defrost on the counter or in water. Fast defrosting can damage your fish. Also, do not keep it in the freezer for months. Couple of weeks is the longest I've tried. Somewhere between 7 days and a few months, fish texture starts to change. It happens at different times for different fish. I try not to test my luck and don't keep fish frozen longer than obligatory 7 days. Also, don't freeze whole fish. The smaller the piece, the faster it will freeze, and the less trauma your fish will undergo.

What about FAS (frozen at sea) or flash frozen fish? FAS is a nice marketing term and no more than that. At sea or not, frozen is frozen. "Flash frozen" is a very fast freezing methodology that is an optimal way to freeze fish -- supposedly, much better than your home freezer. I've never had flash frozen and home frozen fish side by side, so I can't comment on how big of a difference it makes taste wise. I have a feeling that flash frozen stuff can just stay in that state longer than home frozen stuff without affecting the taste, but I've never tested that theory. From my experience the type of fish makes a much bigger difference. I've had excellent fatty fish like Chilean Sea Bass and fatty salmon that have been flash frozen and home frozen and they tasted fine. But I've never had any luck with previously frozen lean fish even if it was flash frozen.

Does this mean that all Trader Joe's fish is sushi grade? It's all previously frozen, right? There is much more to sushi grade than lack of parasites. The quality of the fish, the fat content, freshness at the time it was frozen, and storage conditions all make a difference. The stuff that sat in Trader Joe's freezer for 6 months is not an option for eating raw (at least not a tasty option).

83 comments:

Interesting, I always thought you had to deep-freeze fish to kill all the parasites for sushi. Whenever I make sushi at home I go out of my way to buy "sushi-grade" tuna and salmon, frozen from our local Japanese grocer.

Maybe this isn't true, did you come across the deep freeze debate in your research?

According to FDA, freezing fish to -20ºC [-4ºF] or below for 7 days or -35ºC [-31ºF] or below for 15 hours will kill the parasites. Here is a link to their website. A normal home freezer is at -20ºC [-4ºF], so you just have to keep it frozen longer (7 days instead of 15 hours). Also, note that "sushi-grade" is a marketing term in US. In other words, it's not regulated and doesn't really mean anything. The only rule there is about "sushi-gradedness" is that fish that has not been previously frozen cannot be sold as "sushi-grade." For example, one market might label their tuna as sushi-grade and another might not. The one that is labeled sushi-grade is not necessarily safer or tastier whatsoever. Harmful parasites in large tuna (yellowfin, big-eye, and bluefin) are almost non-existent, so what you really have to worry about is bacteria. And that's just freshness. For example, in Cambridge, where I live, there is a Japanese market that sells "sushi-grade" fish and an Italian fish market where I shop. All fish at the Japanese market has been previously frozen, but it never tastes nearly as fresh as the stuff I buy from my fish market. Who knows when they defrosted it and how long it sat there. So, the bottom line is, you can't just look at labels like "sushi-grade" as a blessing to eat raw fish. For the best possible product, you have to find a knowledgeable fishmonger. Your Japanese grocer might be such a source. But just because they are Japanese and only sell previously frozen fish does not make any guarantees about the quality.

Wow thanks! That is so helpful. I admit I haven't made sushi at home since moving back to Vancouver we are so blessed with affordable quality raw fish at every turn that it seems silly to try and replicate it at home - but you have given me new confidence.. and maybe come salmon season I will try this!

Tilapia is pretty firm, so it might deal with freezing relatively well. I've never tried it previously frozen, so I can't say. Basically, if the fish is firm when you press into it and springs right back, it's fine.

This is a slightly different take on the frozen fish debate. An Australian study found that the most common frozen fish products had low levels of omega 3 fats. http://www.choice.com.au/viewArticle.aspx?id=105077&catId=100286&tid=100008&p=1&title=Test%3a+Frozen+fish

Now they were talking about the supermarket packaged fish, very different to sushi quality but it was interesting. It also showed that weight for weight fresh fish was cheaper than the frozen ones.

What an interesting take on frozen fish! Just to clarify for other readers -- freezing does not diminish the amount of omega-3 fatty acids in fish. The website we are discussing talks about frozen fish *products* (like fish sticks and already cooked entrees), not just plain frozen, uncooked fish. It happens so that the fish mostly used for fish products are white mild fish that don't have much omega-3 to begin with. But those salmon entrees the site listed are full of omega-3 even if they were previously frozen.

About the price per pound. Frozen uncooked fish is generally cheaper than equivalent fish that was not previously frozen. But when it comes to fish *products*, a lot of what you are paying for is packaging and prep. In other words, the fish you get in a fish stick package costs more per pound than if you were to buy that fish (even not previously frozen) and make fish sticks yourself. That's understandable for any prepared product.

I just don't want people to take away that "fresh" fish is cheaper than frozen and that freezing destroys omega-3 fatty acids.

I love salmon, especially sushi, but didn't know until I moved to the Pacific northwest about the issues surrounding farm-raised salmon. it seems common knowledge out here that farm raised salmon are not as healthful for you, for the environment, for wild fish, and contain PCBs, antibiotics, colouring, and have less Omega3s than wild salmon. There's tons of information on the issue, at places like http://www.mbayaq.org/cr/SeafoodWatch/web/sfw_factsheet.aspx?fid=133>monterey bay aquarium for instance.

When it comes to fish, "common knowledge" is unfortunately often wrong. I realize that there are tons of environmental sources that make it look absolutely terrible, but many scientists still think that the benefits of eating farm-raised salmon outweigh the risks big time. It's absolutely not true that farm-raised salmon has less omega-3 than wild. it all depends on the species. Wild coho and sockeye salmons for example have way less omega-3s and wild king salmon has more. If farm-raised salmon is bad for the environment, it's because we want it to be dirt cheap and not because farm-raising fish is fundamentally bad. Not all farm-raised salmon is treated with antibiotics. Besides most of the chickens are treated with them too :) The bottom line is: it's important to consider your source's agenda and to take everything you hear in the media with a grain of salt (including what you read on Beyond Salmon). And to be straight forward, I'll lay my agenda out for you. I am a cook and a relatively healthy conscious person. Thus my first priorities are how good does it taste and is it good for you. In that regard, I am a huge fan of good quality farm-raised salmon. It's extremely fatty, tastes great, safe to eat raw (if you obtain a high quality, very fresh fish), and packed with omega-3s. There is no proof that the slightly higher levels of PCBs cause any harm since they are still only present in tiny amounts.

The issue of farm-raise vs. wild already came up in the comments on this post. See my reply in the comment right before yours. Basically, it has nothing to do with farm-raised vs. wild. It has to do with the species of salmon. Coho and sockeye are wild and have way less fat (thus less omega-3) than atlantic farm-raised salmon. But king salmon whether wild or farm-raised has more fat than atlantic farm-raised.

Another excellent article. Your site is great, and emboldened me (an amatuer chef) to finally try grilling a whole fish. In Southern NH there are not any great fish markets, but next time I am in Cambridge I will try your suggested fish market. I picked up a nice 1.2 lb whole frozen red snapper. It came gutted, and partially scaled and partially cleaned. I finished the job the fisherman started.

I borrowed a technique from another cook on your site, who mentioned salting both sides of the fish, letting it sit while preparing to cook, then rinsing off the excess and seasoning again this time only to taste with salt and pepper.

I olive oiled both sides and stuffed the insides with long strips of scallions and ginger.

I put the fish on the hot grill and used your techniques for timing and flipping.

Meanwhile in a saucepan, I heated some mashed ginger and chopped scallions with peanut oil. When soft, I removed from heat and added soy sauce, dark soy sauce, and a tiny sesame seed oil.

Removing the fish from the grill, I drizzled the dressing over it inside and out and let it sit.

I'm delighted to say that it tasted delicious with a side of parboiled rice. Thanks so much for your helpful information and dedicated experimentation.

I've not done a side by side taste test, but in terms of texture, it makes sense that fish frozen at sea would be better than fish you freeze at home, because of the more powerful freezer. What causes the change in texture when you freeze fish is the rupture of the cell walls due to the formation of ice crystals - and so the way to preserve the texture is to freeze the fish as fast as possible, because this minimizes the size of the ice crystals that form. (this is all paraphrased from Harold McGee) - what I'm wondering about now is the fact that, as far as I know, most tuna sushi is frozen at sea, simply because they're deep sea fish that can't really be caught by dayboats...

I've read all this stuff before in food science literature and I am sure it's true. But from my personal experience and after talking to sushi chefs, I realized that different fish freeze differently. Fatty fish do great with it and lean fish don't. How long the fish is frozen makes a difference too and some sushi chefs actually prefer to freeze the fish themselves rather than buy it already frozen (this way they are guaranteed that the fish is only frozen for a short period of time). The fact that all tuna is previously frozen is a common misconception. It's not and neither is swordfish. Huge fish like that can stay on ice for weeks and keep perfectly fine without freezing. The stuff that gets shipped to Japan or goes to sushi restaurants is often frozen, but the main reason for that is to avoid price fluctuations.

On another hand, I've bought frozen at sea halibut before and it was horrible. Of course, it was from trader joe's, so maybe that's just a bad place to buy fish in general. But previously frozen sockeye or coho salmon from Whole Foods is pretty bad too, while previously frozen Chilean sea bass, also from Whole Foods, is fabulous. So I have a feeling that the fat content has much more to do with it than the freezing method in spite of what conventional wisdom says.

Currently, Trout Unlimited is working on a Pacific Salmon campaign, with one goal of educating Salmon consumers about that choice. TU is looking towards salmon consumers as a tool for the protection and creating a sustainable population of salmon. TU wants you to eat and enjoy wild salmon--but to do it an a manner which encourages sustainable populations.

Trout Unlimited believes that the influence consumers have on protection of critical habitat, clean water, free-flowing rivers, sustainable fisheries, responsible hatchery management will be so great that action will be taken to ensure all of the above.

I buy my salmon fresh in large quantities and freeze it myself in portions I choose immediately. When thawed, it is about as good as the day you buy it as long as you defrost carefully. I defrost in water baths and move to fridge, and with the salmon I use colder/room temp water, cause warm water will start to warm the fish and by the time I cook it, well, it's just not as good. I have bought some already frozen salmon and not liked it, raw or cooked. I have some defrosting as we speak, waiting to be fried in a sesame seed crust and drizzled with wasabi sauce!

Hi Helen,I recently visited a chinook (king/spring) salmon farm in Tofino, BC. Having personally validated the concerns raised against fish farming, I am in agreement that, indeed, the so-called "common knowledge" about farmed salmon is slanted to sway public opinion into an avoid mode. I will soon apend a video clip on the current article,

Hi, I'd like to put in my two cents on the farmed/wild debate. I think that farmed salmon is a valid substitute for wild salmon, but there are several things to consider. I'll just address the two comments made earlier.

I.Omega-3 levels may indeed be lower in farmed salmon due to feed concentrations. The high level of good fats in wild fish comes from the consumption of lower trophic level fish such as herring and sardines. Fish farms are currently struggling with the high prices of fishmeal and are moving towards use of plant proteins such as soy and corn. The change in diet will make salmon more closely resemble terrestrial meats such as chicken or beef.

Here is a story about the National Oceanographic and Atmospheric Administration push towards conversion to plant based proteins:http://www.noaanews.noaa.gov/stories2007/20071116_aquaculture.html

II.

Readers should be conscious that Chile produces over 60% of all farmed Atlantic salmon entering the United States while Canada produces less than 15%.

(I eat farmed salmon, but it's important to be informed about your decisions)

Im glad to see others tackling the frozen vs fresh issues. I also eat vacuum sealed frozen wild salmon 1 months per year and it tastes better than so-called "fresh" fish found in large chain stores. Sometimes this has been outta the ater for 4-5 days...yuck! Frozen is better 9 out of 10 times, IMO.And yes, sushi should be frozen prior to eating for the fore-mentioned parasite reasons

Depending on where you live, frozen might or might not be better. In Boston or anywhere on the coast or in a large city that has a good demand for fish, there is some wonderful fresh fish if you go to a good fish market. But I realize that it might not be the case everywhere. About fish being out of the water for 4-5 days before being sold. That's perfectly normal as long as it was stored on ice. Some fish, like cod, aren't even good to eat for the first 3-4 days because they go through rigamortis. Fin fish is not nearly as perishable as people think it is. I don't know of any fin fish that won't last perfectly well for a week once out of water if left whole and stored on ice. Some, like tuna and sword will last for couple of weeks.

How long is fish good frozen, generally? I'm a college student and live in a house with eight girls. I was cleaning out the freezer and found some frozen salmon from one of the girls who moved out this past fall. It's from Trader Joe's and was bought frozen, but there's no sell-by/use-by date.

it all depends on what you mean by "good." I don't think it will make you sick, but I can pretty much guarantee it won't taste very good. Frozen fish from TJ is not great to begin with and this one probably sat in the freezer for months. How long a fish can be in the freezer before it's texture is effected depends on the fish. Some fish can't be frozen at all, others will last couple of months. I don't have any data on how long different fish will last, but what you found is probably a year old if not more. If I was in college, on a tight budget, and really needed to eat, I'd cook it (I was there once, so I understand) But don't expect a culinary revelation ;)

I am here to lend my professional insight to this debate- fascinating topic. I agree with Tse-Wei aho said that ice crystals can be made smaller if you freeze it very very quickly- metallurgical fact- yes I am a materials doctoral student! So it would make sense that a fish flash frozen at sea would last longer, preserve taste and texture than if you were to do the same thing at home. Also I agree with Helen that you should never defrost meat or fish or any food for that matter very quickly- i.e. do not microwave, or on your counter top. This is as far as scientific knowlege goes- I have tried frozen and fresh fish- caught an hr or 2 before (back at home in India)- and conclude fresh is always best-even the fatty ones. I have no idea with sushi or eating raw fish- not exactly my cuppatea!

Hmm... I ran across frozen sardines in the freezer section at Star Market today. (I didn't look at the label too closely, but they were gonsalves brand, so I'm assuming they're Portuguese.)

They're a fatty fish, which bodes well for the freezing process. But since they are sold in bags in the supermarket, rather than from a proper fish market, I'm sure they've been frozen for more than 7 days. I wonder if they'd be worth a try, at least as my backup stash. (i.e., for when I'm too lazy to walk to New Deal)

7 days is the minimum amount of time you have to freeze fish to kill the parasites. It's not the maximum. Those sardines are definitely worth a shot, but I don't think they'll come close to what you get at New Deal.

I've been trying to find information on the production of botulism toxins in vacuum packed salmon. This is my concern: A careless employee neglects to immediately transfer the frozen product to the freezer in the store. This then allows the product to reach temperatures in the living rage of the spore. I buy the product and die from eating it. Is this a real concern? I've read the heating the botulism toxin would defect the poison, but will heating the salmon to the needed temperature to destroy the toxin also damage the omega 3s and other beneficial parts of the fish?

I haven't heard of botulism being a risk in frozen fish. If you worry about that, you might as well worry about botulism in canned products and never buy anything in a can. Botulism mostly comes up with home canning and curing. Don't worry. Eat fish (not frozen whenever possible - not because of safety, but because it tastes good), don't overcook :)

Interesting write up. I have a point to add. For large Tuna (Yellowfin/Big eye), the latest trend is 'super freezing' at -60C. Have you heard of this? This product is meant for 'raw consumption' and very popular in Japan

Yes, many fish intended for sushi are frozen to manage supply/demand issues. The fatty ones can freeze quite well. I am guessing you meant "Bluefin" not "Yellowfin." Yellowfin is very lean and not particularly prized in Japan. It's also available year round, so there is no need to freeze. Bluefin and big-eye can be wonderfully fatty (some times of the year), and are worth freezing.

I write food review columns and recently I was sent dozens of free samples of frozen wild Atlantic Salmon from a top notch company in Bellevue, WA (as a matter of fact it was a dream come true).

Anyhow, while the king Salmon was the best (and is about twice as expensive) the flash frozen fresh Sockeye was also excellent. They all rated 10 out of 10 by several testers, and each was served raw and cooked. The mushiness especially applied to smoked frozen Salmon, which was Spam-like.

The skin-on is cheaper and the skin can be easily removed when the fish is still frozen by slicing into it and peeling it off in one piece.

Thanks for your article, very insightful! I'm a college student and I just bought a bag of frozen salmon from costco, it has each portion individually vacuum-sealed. I was planning to bake it, but now I have a terrible craving for sushi. Do you think its okay to eat this type of frozen salmon raw after I defrost it in the fridge? Thank you!

No, it's absolutely NOT ok to eat fish raw just because it was previously frozen. Freezing takes care of parasites, but not bacteria. You have no information on how long this fish was kept in the frozen state and how it was handled before freezing and during its potentially lengthy freezing period. Defrost your salmon in the fridge overnight (the slower you defrost, the less you'll harm the texture), and cook it.

This is all great information. I have recently had a significant heart scare and want to eat more salmon. However, my local grocer in upstate NY has only a fair fish counter. Are any of you aware of good mail order suppliers? I've done a little research and found a few, but the fish tends to run about $20/pound. Many thanks - PSP

It could be either, but a fishmonger needs to tell you that it is fresh enough to serve raw. generally, fishmongers that are knowledgeable enough won't carry frozen salmon. the only exception to that is salmon specifically labeled "sushi-grade" like at Whole foods. that means it was frozen for a certain amount of time to kill parasites.

freezing doesn't suddenly make it "safe." It only addresses the parasite risk, not the bacteria risk. Find a fishmonger that caters to the raw fish crowd and has many raw fish customers and ask them what they recommend. I realize that it's not possible in some parts of US.

I would like to take a moment to address FAS vs home freezer. I have had the opportunity to try both, and there is a remarkable difference between the two. The FAS Alaskan sockeye and coho stand up much better than the home frozen products. I have been freezing my salmon in the freezer at home since I was a child. Living in Alaska most of my life lent me the opportunity to catch quite a lot of fish, and we have always frozen the fish. Since moving near the Purdue campus in Lafayette IN, I have not had access to the seafood I am used to.

I had relatives send some salmon since the only thing I could find around here was the tasteless farm raised salmon. I have since opened a store that has only supplies ONCE frozen wild caught seafood products. Back to the point, I have had the opportunity to cook both at the same time and there is a definitive difference in the texture between the two.

In regards to farmed products. You state that you prefer the farm raised salmon to the wild caught due to the high fat content. Does it not bother you that it takes 2 to 3 pounds of wild caught feeder fish to make 1 pound of farm raised salmon? Or that in the pellets that are fed to the farm fish has soy and wheat by-products in them. Or that in the farmed salmon process is that they have to add dye to the food, or else dye the fish after harvest in order for it to have the correct color.

There has been numerous tests confirming that the mercury and PCB levels are higher in farmed salmon than wild caught. The USDA recommends that you should have 2 to 3 servings of fish per week in order to maintain a healthy diet, but it also stated in that report, that depending on where the farmed products come from, you should not have more than two servings per month because of the mercury and PCB levels.

I do commend you on educating those who are unaware of the positive aspects of frozen vs fresh. Thank you for the time and space on your blog.

Great information but I must add that being married to a longliner and learning the process I have learned that it matters how the fish is caught as well as how it is frozen.

-longlining and jigging are the two most sustainable ways to fish.-Fish that are caught by a hook or jig get processed and Flash frozen right than and there on the deck. The ones that are netted or trawled are at times left on the deck or caught in the net and it can be an hour before they are removed and bruised as well. The prime catch of these two types of fishing are not sent to the US market they are sent overseas. I also learned that when you flash freeze it seals in the freshness and if its than put in a home freezer its taste will be great. Its the waiting and letting the fish hit rigor mortis and than freezing it, is what leads the reputations of "Bad frozen Fish".

So keep in mind its how the fish are caught, and how they are frozen before processed. Also, Farm raised fish are not as sustainable nor as natural as you may think.

In regards to your question about the product your wife purchased, it is most likely a farmed product. The thing you need to check next is the country of origin. If it is from China, I would thoroughly investigate the production facilities. A good rule of thumb, based on my research, avoid farmed fish from China. The reason I am suggesting that is because of the lack of strict regulations in the raising or processing of seafood from there. (mind you, there will always be acceptions)

I do not have a Costco close to me so I am not able to help directly with any answers.

I am a firm advocate against the farm raising of salmon because of the depletion of the oceans of the feeder fish that the wild salmon are in need of in order to be survive. Surely with the science available today, they can come up with a viable resource other than the wild feeder fish.

Anyway, bottom line is, do the research. USDA regulations require that the country of origin be placed on the packaging, as well as the packing plant. Feel free to contact me directly if you are in need of help.

Althought I'm not Spencer's wife, I bought the same fish she had bought from Costco. As far as where that fish came from - I saw on the packaging that came from Boston, MA. Which I also read that is a good place to come from. I guess...

Ok, everyone buying fish at costco to use for sushi -- it's not the best idea. nothing against costco -- they carry some good products, but if the fish is not intended for raw consumption, you shouldn't be using it for raw consumption. Here is a rule of thumb with eating fish raw -- you should talk to a fishmonger and have him confirm that it's a good fish to eat raw, otherwise you are taking a bigger risk.

Since last post was 2007 I doubt this thread is still active but thought I'd give it a shot.

My question is why do you seem to favor frozen sushi grade fish from Whole Foods over Trader Joe's? Do you know for sure that Trader Joe's fish has sat in the freezer for months and the fish at Whole Foods hasn't?

I know for sure that the fish Whole Foods sells as "sushi grade" will not make you sick. I can't say the same about Trader Joe's. It's a gamble. I've never tried Trader Joe's fish raw, but I tried cooking it and it's really quite awful.

Just what I needed. I'm about to eat some fish tonight, I thought that all fish could be eaten raw... I forgot about BOTH parasites and bacteria. Good thing I did a little research first! Thanks, steamed it is until I get some good sushi grade salmon or tuna!

I would take issue with your comment that frozen Sockeye turns to mush. This years Sockeye harvest was the best/largest since 1913. I have been finding high quality fish portions at Costco for months now, these looked so good I took to eating them sashimi and negiri style and they have been amazing. My wife's concern has been about safety, but since these are coming from Alaska and flash frozen I don't share her concerns. Sergio in San Diego

Consider: Fresh fish that was caught commercially is often stored in an iced-hold for up to a week before being delivered to port. After that, it must go through a distribution system from wholesaler to retailer, all before it is sold as "fresh" fish. Iced fish is not frozen fish. You can make an intelligent guess as to how it has been since your "fresh" fish was caught. I've worked on a salmon trawler ... I buy my fish frozen every time!

the fish that was farmed is usually harvested and shipped to the whole saler immediately. A whole saler of arctic char told me that their fish is usually out of the water about 5 days by the time I buy it, which is not bad at all.

also, keep in mind that not all fish on the boat gets priced the same way. the later it was caught -- the higher the price. it's known as "top of the catch."

I live in Boston and have access to a lot of fabulous not previously frozen fish. it's not because we are on the coast. fish trade is global now. some of our fish come to us from europe and the west coast. it's just because Boston has a serious fish culture in the markets and restaurants.

keep in mind that not all "frozen" fish is created equal too. some of it was frozen, shipped to China, defrosted, filleted, refrozen, and shipped to the US.

there is some wonderful previously frozen fish (rarely available for retail) and some wonderful not previously frozen fish. from my experience, previously frozen stuff usually pales in comparison unless the fish is either kept in a super freezer (used by sushi restaurant suppliers) or is very fatty (like Chilean sea bass).

Thank you for the good info. You mentioned something about yellowfin can be iced for weeks? Are these still good for sashimi grade? I notice the colour of yellowfin tuna deteriorates after thawed. Please advise. Thk you

Sorry I have to disagree with you in the sense that Sockeye and Coho will freeze beautiful if it's freeze the right way.I live in Alaska, so I know. we eat fish all year long...The way to freeze Salmon is the day is catch.My own personal experience...

As previously mentioned, it does depend on the fish. I work as a Chef Saucier in a fine dining restaurant, as such, one of my main jobs is maintaining and cooking fish. I have had tremendous results with freezing Halibut. We buy it whole, break it down, filet it and freeze it in out large and very efficient deep freezer. I have had good results with about eight different species of Snapper, as well as Pompano, Triple Tail, and a long list of others, Salmon and Grouper included. That being said, I prefer not to freeze if at all possible. The condition of the fish before freezing is a major factor, and if it is already in less than optimal condition, the effort will not be rewarding. Also, once defrosted, it cannot be re-frozen, which is something that I have seen done before. Unfortunately I do not have access to the suppliers I use at work for purchasing fish at home, and the majority of what is sold in my area fresh is Catfish and Tilapia, so I have to buy frozen. The only way to do this with good results is by doing your research. On a final note, stay away from Chilean Seabass, more properly Patagonian Toothfish, as they are over fished, and although not officially listed as endangered or threatened, they are most likely heading that way very rapidly.

Fresh fish is always better than frozen one but due to time and geographical constraints, you cant do without the frozen fish. Here is how you can change your handicap into an advantage: http://www.ifood.tv/blog/tips-to-cook-frozen-salmon

Thanks for the info, I had a friend who thought that fresh fish was inedible because of toughness or something like that (but that did not make sense to me).

On the topic of flash frozen fish, and just anything in general. I know a little from a physics standpoint.

Normally frozen watery material (beef, fish, fruit) will be damaged from freezing because the water expands into sharp spikes cutting the object on a microscopic scale.But properties like lots of fatty tissue can reduce the overall damage (or at least appearance of the damage).

Flash freezing produces a very different result. When something is frozen near instantly the water does not have a chance to expand and damage the fish (meat, or fruit) and when thawed remains relatively identical to before freezing.

Great info, and I apologize in advance if this seems like the same question over again. Mine is with respect to farm raised salmon bought from a reputable grocer chain (Henry's, Sprouts, Whole Foods, etc.). The salmon I bought was sold as "farm raised, fresh, from Canada". So it was not frozen (so they claim). I've also seen similar salmon sold at Costco (as opposed to the frozen variety). Do you think that it's safe to eat this particular salmon raw? It's been in the freezer for about 7 days now...

The only person who can tell you if it's safe or not safe is the fishmonger. I have no idea what this salmon has been through :) having it in the freezer for 7 days takes care of parasites, but who knows how much bacteria is on this salmon.

Many "salmon farms" are placed near river mouths to take advantage of the water currents. This practice endangers the surviving natural salmon runs by exposing wild salmon going to and from their natural habitat in the river to concentrated waste products, bacteria, parasites, antibiotics, etc.

I just wanted to say that you have done amazing research on fish husbandry, nutrient components, and preparation methods. It gives me faith to know people are out there who really educate themselves on animal products. Thank you for your lack of ignorance. From a very greatful animal scientist.

Hi Helen, 'bacteria' has been mentioned quite often in reference to the frozen fish. So... how does the fishmonger take care of the bacteria? You say he knows whether the fish is suitable for raw consumption..... Thanks

The way a fish monger takes care of bacteria is keeping fish on ice the entire time, filleting as close to time of sale as possible (bacteria need oxygen to grow), and selling fish quickly enough so that bacteria count is low enough. Fish mongers that specialize in fish for raw preparations will also know which fish are prone to parasites and will advise you to avoid them for raw dishes.

I'm so glad someone mentioned the farm-raised salmon issue. It's funny when a person who is educated or "don't like being wrong" is wrong but they pretty much just make stuff up as they go based on their own opinion. Sorry, nothing will ever be better than wild caught salmon. If you don't think so you need to really think about the basic idea of the matter.

I have to add a comment here because this issue is really up my alley and important to me. I've been living in Alaska for nearly 30 years, and have been putting away salmon, halibut, shrimp, and other fish away every year. Fairly recently however, because I've gotten lazyier, or value my time more, I 'discovered' flash freezing services. I now have my fish commericially flash frozen whenever possible, and it makes an ENORMOUS difference in longevity of quality. I used to not be able to stand the taste of salmon frozen more than 2 or 3 months. Now I'm enjoying salmon 9-11 mos later. Halibut was always a good freezer fish, but really starts to get sour after 6 mos. Flash frozen its good for over a year. I also have a commercial grade freezer (not a self-defroster) that I store my product in at about -10 F. As far as fresh vs frozen goes, yeah, fresh is better, but you better know what the definition of fresh is. For me, unless that fish has been on ice since caught for no more than 3-4 days, it is not fresh. And there are very very few markets that sell fish, that I know (unless live caught/sold) that can do that. I tell people, if you have the choice at a supermarket, go with frozen, cause you have no idea how long that fish was "fresh".

I had before not considered the importance of choosing the right breed of salmon to freeze if I want to maintain good taste. I personally find fresh seafood to taste incredible; getting it from the right place is important. When it is being farmed you want them to have things regulated and have the consumer's best interests in mind.http://www.gulfshoressteamer.com/about.asp

I prefer wild alaskan salmon for making sushi. I buy frozen then thaw and soak in a mild salt & rice vinegar for a half hour rinse and walla! Most of the farm raised salmon I see at the store looks bland, no color! I'm not sold on farm raised ! It's America ,use what you want,it's your body.

I have frozen farm raised salmon due to large amount you have to buy at big box store which is way to large for my small family. I am not a scientist but have never been able to enjoy frozen farm raised salmon from my freezer, and discarded it. I am not sure it is due to Ice Crystals or what. I have even tried to freeze small amount of water in a shallow long container before buying salmon and then wrapping piece of salmon in wrap, 2 times then placing it on top of the frozen water and waited and very slowly added little more water all day till fish was covered. I defrosted it in the frig. but at this point couldn't get myself to cook and taste it and discarded it.I was trying to freeze it faster. Wish there was a freezer for home use that has a area to flash freeze. On cruise ships I am ok with the fish and can eat it but not happy with freezing at home. Maybe I should try my new freezing method again and this time cook and taste it. I feel bad just discarding half the fish I buy and where I trust the freshness from this big box store better than my local fish stores. Has anyone else tried other methods to try to freeze fish faster. Should I cover the fish with one layer and then place it directly onto the ice. should i add water little at a time to cover it or not? How should I defrost it at this point. I am trying to be creative in freezing faster. I would like to hear from anyone else that has tried this or other way to freeze salmon or other fish faster than a regular freezer can and your thought on this. Or if you came up with another idea? Can we invent a way to freeze fish better with a residential freezer?

Water is the enemy when freezing. I would definitely not recommend freezing fish directly in ice. You want it wrapped tightly in plastic. The problem with your home freezer is not the speed of freezing as much as constant defrost cycles. Don't keep salmon there longer than 2 weeks and the quality will be decent. You might also be able to keep it in the fridge covered with ice-packs for 2-3 days. No need to eat it all the first day. Flash freezing is not just about freezing fish faster. It's about freezing it to much colder temperatures (-40 instead of 0F). It's impossible to recreate at home.

I must admit when my husband comes home with fresh fish he caught it definitely is the most tasty that night. I love your ideas for freezing fish for later. One site I often use for cooking ideas is cookingchart.com for fish and other foods.

Freezing my fresh wild-caught sockeye salmon has become necessity here in Nashville TN. And great that serving sizes when thawed and quick cooked pan fried retain the colour shape and texture and taste of fresh.

If you would allow me, I would like to give you my opinion on Frozen at Sea Salmon. I am a Salmon Troller. We fish in the gulf of Alaska, all along the southeast coast. So as not to be confused with Trawlers, vessels dragging nets that are highly destructive to all sealife, we troll with as many as sixty hooks at a time in the water. Every salmon we take that is legal is immediately headed, gutted and bled. We use a special process , called pressure bleeding that eliminates 100% of the blood in the fish. That fish is placed below and frozen to a core temperature of minus 40 degrees. After several hours of this the fish is dipped into a saltwater bath with our on added glaze ingredients which forms a protectve coating over the whole fish. The first freezing stops the fish from going onto rigor mortis so there is absolutely no deterioration of the quality. This fish is truly fresher than fresh. This method assures the salmon is really sushi grade. The water it comes from is far from any fresh water which is the death knell for salmon. As soon as they encounter any fresh water , like gettin in close to the rivers, the deterioration cycle begins. That is where your fresh fish is generaly caught. It is held in fish holds for as long as five days in bloody slushy ice and water and then sucked up hoses and into a sorting area. They then are put back into ice and held until shipped. Then trucked to market. Your fresh fish may be 2 to 3 weeks before it hits your plate. For more information go to our facebook page at harman & sons fishing co. Also go to the Alaska Seafood Marketing Institute web site and pay particular attention to the cook it frozen section. As far as the farm raised salmon go just think about thousands of fish jammed into nets in the ocean breathing and swallowing all the fecal matter and bacteria they create. That is why antibiotics are used to keep the fish alive. Many of these fish are dyed to give a red color. These farms are a threat to our ( the U.S. ) wild stocks either by spreading disease or escapment. Help Alaska and Alaskan families by buying only wild caught Alaskan Salmon. From our family to yoursDave HarmanHarman & Sons Fishing Co.Douglas, Alaska

Hi Helen,First off, thank you for your hard work with your blog. I realize the article above was written in 2007 but information doesn't die on the internet and it's now 2016. Please for the sake of your fans, our environment and our future in eating salmon, brush up on the real issues of farmed versus wild salmon. Here is a YT film that breaks it down. https://www.youtube.com/watch?v=MTbxOFcvC4UThank you.

I know it's 2016 now and this timeless article is from 2007 but just for the record, i am from Asia, and a place where we have access to fresh fish all year round. And fresh always taste best. Any excess we bought will be placed in the freezer. Even if just after a day frozen, when we take it out to cook, it will lose that taste compared to fresh.